European Patent Application EP 429 366 has described antagonists of substance P having the structure: ##STR3## in which the symbols R are hydrogen or together form a bond, the symbols R' are optionally substituted phenyl radicals and the symbols R.sub.1 and R.sub.2 represent various substitutions. However, these perhydroisoindolone derivatives have been found to be active mainly in binding tests using rat brain homogenates, and display less activity in binding tests using cultures of human lymphoblast cells.
U.S. Pat. No. 4,042,707 had described products derived from isoindole, of the general formula: ##STR4## having an opiate activity. These products do not have any activity against substance P.
To date, in spite of research carried out and in spite of the abovementioned interest [M. R. Hanley, TINS, (5) 139 (1982)], no product which acts specifically on substance P and has a nonpeptide structure had been discovered in practice, and for this reason the isoindole derivatives of the general formula (I) are of considerable interest.